Abstract: Cancellation of a leaked transmission signal received together with a received signal is cancelled at a receiver amplifier in a system made up of the receiver amplifier, a power amplifier, and a duplexer that couples both to an antenna. A portion of the amplified transmission signal from the power amplifier is split off prior to the duplexer. That portion is controllably applied to the receiver amplifier. A feedback loop monitors the amplified output of the receiver amplifier and varies the gain and phase of the portion of the amplified transmission signal in order to minimize the amount of transmission signal in the amplified output of the receiver amplifier.

Abstract: A signal cancelling duplexer is provided. Duplexers of the invention add equal amounts of a transmission signal and an out-of-phase component of the same transmission signal at the receiver, so that both signals cancel. Duplexers of the invention can be switched between multiple channels by changing switch settings within the duplexer. RF transceivers including a power amplifier, receiver amplifier, and the signal cancelling duplexer are also provided.